Responses of Wetland Ecosystems to Drought-Induced Fish Eliminations

Abstract

Landscape alterations can alter fish occurrence and abundance in wetlands. By increasing turbidity in wetland ponds, fishes can induce a shift from a clear- to a turbid-water state, resulting in reduced plant and amphibian abundance. In 2012, a drought reduced water levels and eliminated fishes from many wetlands of the prairie-pothole region (PPR) in the Midwestern United States. Our study objective was to evaluate if fish eliminations were associated with changes in wetland condition. A one-way ANOVA was used to compare the magnitude of change in parameters indicative of wetland condition (turbidity, plant cover and taxon richness, and tiger-salamander (Ambystoma tigrinum) biomass and numerical abundance) from 29 Iowa PPR wetlands between 2010 and 2011 (pre-drought) and 2014–2015 (post-drought) among wetlands where 1) all fishes were eliminated 2) large-bodied fishes were eliminated, 3) small-bodied fishes were eliminated, 4) fishes were retained, and 5) fishes were never detected. Turbidity decreased and plant cover increased more where large-bodied fishes were eliminated compared to the other groups. Changes in tiger-salamander biomass and abundance and plant-taxon richness were not different among groups. Results indicate that wetlands can shift from a turbid- to a clear-water state following drought and elimination of large-bodied fishes.